Functional polyesters prepared by polymerization of α‐allyl(valerolactone) and its copolymerization with ε‐caprolactone and δ‐valerolactone

We report the ring‐opening homopolymerization of α‐allyl(valerolactone), compound 2 , and its copolymerization with ε‐caprolactone and δ‐valerolactone using stannous(II) catalysis. Although the polymerization of substituted δ‐valerolactones has received little attention for the preparation of functional polyesters, we found that compound 2 may be incorporated in controllable amounts into copolymers with other lactones, or simply homopolymerized to give a highly functionalized, novel poly(valerolactone). The presence of the pendant allyl substituent had a substantial impact on the thermal properties of these materials relative to conventional polyesters prepared from lactones, and most of the polymers presented here are liquids at room temperature. Dihydroxylation of the pendant allyl groups gave polyesters with increased hydrophilicity that degraded more or less rapidly depending on their extent of functionality. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1983–1990, 2002     

Novel synthesis of biodegradable linear and star block copolymers based on ε‐caprolactone and lactides using potassium‐based catalyst

Biodegradable, triblock poly(lactide)‐block‐poly(ε‐caprolactone)‐block‐poly(lactide) (PLA‐b‐PCL‐b‐PLA) copolymers and 3‐star‐(PCL‐b‐PLA) block copolymers were synthesized by ring opening polymerization of lactides in the presence of poly(ε‐caprolactone) diol or 3‐star‐poly(ε‐caprolactone) triol as macroinitiator and potassium hexamethyldisilazide as a catalyst. Polymerizations were carried out in toluene at room temperature to yield monomodal polymers of controlled molecular weight. The chemical structure of the copolymers was investigated by ¹H and ¹³C‐NMR. The formation of block copolymers was confirmed by NMR and DSC investigations. The effects of copolymer composition and molecular structure on the physical properties were investigated by GPC and DSC. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5363–5370, 2008     

A novel and versatile potassium‐based catalyst for the ring opening polymerization of cyclic esters

Poly(lactide) (PLA), poly(ε‐caprolactone) (PCL) and poly(trimethylene carbonate) (PTMC) homopolymers of high molecular weight were prepared using potassium‐based catalyst. Polymerizations were carried out in toluene at room temperature. The chemical structure of the polymers was investigated by ¹H and ¹³C NMR. The physical properties investigated by GPC and DSC for the polymers obtained are similar to those prepared using tin octanoate based catalyst. Using a sequential polymerization procedure, PLA‐b‐PCL, PLA‐b‐PTMC, and PCL‐b‐PTMC diblock copolymers were synthesized and characterized in terms of their composition and physical properties. The formation of diblock copolymers was confirmed by NMR and DSC measurements. In vitro cytotoxicity tests have been carried out using MTS assay and the results show the biocompatibility of these polymers in the presence of the fibroblast cells. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5348–5362, 2008     

Crown‐like macrocycle zinc complex derived from β‐diketone ligand for the polymerization of rac‐lactide

Enolic Schiff base zinc (II) complex 1 was synthesized. XRD revealed 1 was a novel crown‐like macrocycle structure consisted of hexanuclear units of (LZnEt)₆ via the coordination chelation between the Zn atom and adjacent amine nitrogen atom. Further reaction of 1 with one equivalent 2‐propanol at RT produced Zn‐alkoxide 2 by in situ alcoholysis. Complex 2 was used as an initiator to polymerize rac‐lactide in a controlled manner to give heterotactic enriched polylactide. Factors that influenced the polymerization such as the polymerization time and the temperature as well as the monomer concentration were discussed in detail in this paper. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 643–649, 2008     

Preparation and characterization of chitosan‐graft‐poly (ϵ‐caprolactone) with an organic catalyst

Chitosan‐graft‐poly(ϵ‐caprolactone) was prepared via the ring‐opening graft polymerization of ϵ‐caprolactone (CL) through chitosan with 4‐dimethylaminopyridine as a catalyst and water as a swelling agent. The graft content of PCL within the graft copolymer was adjusted by the feed ratio of CL to chitosan, and the highest grafting concentration of PCL was up to about 400%. Fourier transform infrared, ¹H NMR, and two‐dimensional heteronuclear single quantum coherence analyses indicated that the amino group (NH₂ CH‐2) of chitosan initiated the graft polymerization of CL through the backbone of chitosan, and the hydroxyl group (HO CH_2–6) of chitosan did not participate in initiating the graft polymerization. The percentage of amino groups initiating the graft polymerization decreased with an increasing molar ratio of CL to chitosan in the feed, and this was attributed to the fact that the graft polymerization system increasingly became heterogeneous with an increasing feed ratio of CL to chitosan. The physical properties of the graft copolymers were characterized by thermogravimetric analysis and wide‐angle X‐ray diffraction, respectively. These suggested that the introduction of PCL grafts through the chitosan backbone would to some extent destroy the crystalline structure of chitosan, and the PCL grafts existed in an amorphous structure. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5353–5361, 2006     

Organocatalysis applied to the ring‐opening polymerization of β‐lactones: A brief overview

Organocatalysis offers a number of prospects in the polymer community and presents advantages over metal based and bio‐organic methods. The use of organic molecules for performing chemical reactions is not a new concept, and any research into organocatalytic reactions builds on a respected history. Compared to the organocatalysis of large lactones, which began in the early 2000s, the examples presented here will demonstrate that few metal‐free initiating systems had been applied to β‐lactones well before the beginning of the current millennium. These metal‐free initiating systems present indisputable advantages over metal‐based processes. In the following paper, ring‐opening polymerizations (ROPs) of various β‐lactones for the preparation of poly(hydroxyalkanoate)s will be presented, as will the types of mechanisms involved, that is, zwitterionic and anionic, and cationic or supramolecular‐based ROPs. The advantages and drawbacks of the different technics will be discussed in the domain, which, for us, is important in the overall production of bioplastics. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 657–672     

Ring‐opening polymerization of 6‐hydroxynon‐8‐enoic acid lactone: Novel biodegradable copolymers containing allyl pendent groups

This article reports the synthesis and copolymerization of 6‐hydroxynon‐8‐enoic acid lactone. The ring‐opening polymerization of this lactone‐type monomer bearing a pendant allyl group led to new homopolymers and random copolymers with ε‐caprolactone and L ,L ‐lactide. The copolymerizations were carried out at 110 °C with Sn(Oct)₂ as a catalyst. The introduction of unsaturations into the aliphatic polyester permitted us to carry out different chemical transformations on this family of polymers. For example, this article reports the bromination, epoxidation, and hydrosylilation of the allyl group in the new polyester copolymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 870–875, 2000     

Titanium complexes of dialkanolamine ligands as initiators for living ring‐opening polymerization of ε‐caprolactone

The titanium complexes with one ( 1a , 1b , 1c ) and two ( 2a , 2b ) dialkanolamine ligands were used as initiators in the ring‐opening polymerization (ROP) of ε‐caprolactone. Titanocanes 1a and 1b initiated living ROP of ε‐caprolactone affording polymers whose number‐average molecular weights (M_n) increased in direct proportion to monomer conversion (M_n ≤ 30,000 g mol^?1) in agreement with calculated values, and were inversely proportional to initiator concentration, while the molecular weight distribution stayed narrow throughout the polymerization (M_w/M_n ≤ 1.2 up to 80% monomer conversion). ¹H‐NMR and MALDI‐TOF‐MS studies of the obtained poly(ε‐caprolactone)s revealed the presence of an isopropoxy group originated from the initiator at the polymer termini, indicating that the polymerization takes place exclusively at the Ti–OⁱPr bond of the catalyst. The higher molecular weight polymers (M_n ≤ 70,000 g mol^?1) with reasonable MWD (M_w/M_n ≤ 1.6) were synthesized by living ROP of ε‐caprolactone using spirobititanocanes ( 2a , 2b ) and titanocane 1c as initiators. The latter catalysts, according MALDI‐TOF‐MS data, afford poly(ε‐caprolactone)s with almost equal content of α,ω‐dihydroxyl‐ and α‐hydroxyl‐ω(carboxylic acid)‐terminated chains arising due to monomer insertion into “Ti–O” bond of dialkanolamine ligand and from initiation via traces of water, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1230–1240, 2010     

Sustainable,Stereoregular, and Optically Active Polyamides via Cationic Polymerization of ε‐Lactams Derived from the Terpene β‐Pinene

A convenient synthesis of sustainable polyamides, which contain side groups and stereocenters, starting from the biobased small terpene β‐pinene is reported. The polyamides, which are obtained via the pinene‐based lactam via ring‐opening polymerization, show excellent thermal properties, rendering this approach very interesting for the utilization of novel biobased and structurally significant high‐performance polymers and materials. Polymer masses and yields are shown to be dependent on different parameters, and the stereoinformation of the lactam monomer can thus be transferred into the polymer chain. In addition, another lactam side product can also be transformed to polyamides.

     

ε‐Caprolactone polymerization under air by the biocatalyst: Magnesium 2,6‐di‐tert‐butyl‐4‐methylphenoxide

This study investigated the synthesis of the biocatalyst, magnesium 2,6‐di‐tert‐butyl‐4‐methylphenoxide (Mg(BHT)₂) complex, and the ring‐opening polymerization (ROP) of ε‐caprolactone (CL). The complex demonstrates high catalytic activity and controllable of molecular weight for the ROP of CL in tetrahydrofuran at room temperature, even when polymerization was performed under air. Before this study, the polymerization of CL had never been performed using a magnesium catalyst under air at room temperature. Various forms of alcohols with different purposes were also used as initiators with Mg(BHT)₂. The results show that the magnesium complex acts as a perfect catalyst because of its high catalytic activity and control ability without any cytotoxicity in the polymerization of CL, making it suitable for biomedical applications. In addition, nanoparticle formation, cytotoxicity, and phototoxicity of tri‐2‐hydroxyethyl ester [Ce6‐(CH₂CH₂OPCL)₃] were also studied in this article and Ce6‐(CH₂CH₂OPCL)₃ formed nanoparticle can act as a nanophotosensitizer for photodynamic therapy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of periodic copolymers via ring‐opening copolymerizations of cyclic anhydrides with tetrahydrofuran using nonafluorobutanesulfonimide as an organic catalyst and subsequent transformation to aliphatic polyesters

To synthesize polyesters and periodic copolymers catalyzed by nonafluorobutanesulfonimide (Nf₂NH), we performed ring‐opening copolymerizations of cyclic anhydrides with tetrahydrofuran (THF) at 50–120 °C. At high temperature (100–120 °C), the cyclic anhydrides, such as succinic anhydride (SAn), glutaric anhydride (GAn), phthalic anhydride (PAn), maleic anhydride (MAn), and citraconic anhydride (CAn), copolymerized with THF via ring‐opening to produce polyesters (M_n = 0.8–6.8 × 10³, M_n/M_w = 2.03–3.51). Ether units were temporarily formed during this copolymerization and subsequently, the ether units were transformed into esters by chain transfer reaction, thus giving the corresponding polyester. On the other hand, at low temperature (25–50 °C), ring‐opening copolymerizations of the cyclic anhydrides with THF produced poly(ester‐ether) (M_n = 3.4–12.1 × 10³, M_w/M_n = 1.44–2.10). NMR and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectra revealed that when toluene (4 M) was used as a solvent, GAn reacted with THF (unit ratio: 1:2) to produce periodic copolymers (M_n = 5.9 × 10³, M_w/M_n = 2.10). We have also performed model reactions to delineate the mechanism by which periodic copolymers containing both ester and ether units were transformed into polyesters by raising the reaction temperature to 120 °C. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

A “Mitsubishi emblem” tetrauclear aluminum complex containing two unsymmetric N2O2‐ligands and a symmetric NO3‐ligand as initiator for polymerization of rac‐lactide

A novel hydroxy‐, methoxy‐, and phenoxy‐bridge “Mitsubishi emblem” tetranuclear aluminum complex ( 1 ) is synthesized from an unsymmetric amine‐pyridine‐bis(phenol) N₂O₂‐ligand (H₂L¹) and a symmetric amine‐tris(phenol) NO₃‐ligand (H₂L²). Two same configuration chiral nitrogen atoms are formed in the tetranuclear Al complex upon coordination of the unsymmetric tertiary amine ligand to central Al. Complex 1 initiates controlled ring‐opening polymerization (ROP) of rac‐lactide and afford polylactide (PLA) with narrow molecular weight distributions (M_w/M_n = 1.05–1.19). The analysis of ¹H NMR spectra of the oligomer indicates that the methoxy group is the initiating group and the ring‐opening polymerization of lactide follows a coordination‐insertion mechanism. The Homonuclear decoupled ¹H NMR spectroscopy suggests the isotactic‐rich chains is preferentially formed in PLA. The study on kinetics of the ROP of lactide reveals the homopropagation rate is higher than the cross‐propagation rate, which is in agreement with the observed isotactic selectivity in the ROP of rac‐lactide. The stereochemistry of the polymerization was also supported by activation parameters. The introduction of unsymmetric ligand H₂L¹ has an effect on stereoslectivity of polymerization. This result may be of interest for the design of multinuclear metal complex catalysts containing functionalized ligands. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2084–2091     

Experimental and computational studies of ring‐opening polymerization of ethylene brassylate macrolactone and copolymerization with ε‐caprolactone and TBD‐guanidine organic catalyst

The ring‐opening polymerization (ROP) of ethylene brassylate, catalyzed by the cyclic guanidine 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD) is reported. Several experimental parameters were evaluated for bulk ROP process and polyesters, resulting in molecular weights between 3 and 15 kg mol^?1. End‐group analysis by ¹H nuclear magnetic resonnance (NMR) and matrix assisted laser desorption ionization time of flight computational studies supports the dual behavior of TBD, which can act as both a catalyst and initiator of the polymerization process. Under optimum conditions, semicrystalline poly(ethylene brassylate‐co‐ε‐caprolactone) random copolymers were synthesized. Depending on the comonomer content, our results showed a range of melting temperatures between 39 and 69 °C. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 552–561     

Polyester from dimethylketene and acetaldehyde: Direct copolymerization and β‐lactone ring‐opening polymerization

Two ways to obtain aliphatic polyesters (PEs) from dimethylketene and acetaldehyde were investigated. On the one hand, a direct anionic copolymerization was carried out in toluene at ?60 °C. The resulting polymer was mainly composed of PE units. On the other hand, a two‐step process involving the synthesis of 3,3,4‐trimethyl‐2‐oxetanone by [2+2] cycloaddition, followed by its ring‐opening polymerization, with various initiators and solvents, led to the expected PE. Molecular weights up to 9000 g mol^?1 (measured by nuclear magnetic resonance (NMR)), with narrow polydispersity around 1.2, were obtained. These polymers were found stable up to 274 °C under nitrogen and a broad and complex endothermic peak attributed to crystallinity was observed near 139 °C by differential scanning calorimetry (DSC). The crystallinity, measured by X‐ray diffraction, was close to 0.45. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and thermoreversible gelation of dendron‐like polypeptide/linear poly(ε‐caprolactone)/dendron‐like polypeptide triblock copolymers

Dendron‐like poly(γ‐benzyl‐L ‐glutamate)/linear poly(ε‐caprolactone)/dendron‐like poly(γ‐benzyl‐L ‐glutamate) triblock copolymers having 2^{m + 1} PBLG branches (denoted as PBLG‐Dm‐PCL‐Dm‐PBLG, m = 0, 1, 2, and 3) were for the first time synthesized by utilizing ring‐opening polymerization (ROP) and click chemistry. The bifunctional azide‐terminated PCL (N₃‐PCL‐N₃) was click conjugated with propargyl focal point PAMAM‐typed dendrons Dm to generate Dm‐PCL‐Dm, which was then used as macroinitiator for the ROP of BLG‐NCA monomer to produce the targeted PBLG‐Dm‐PCL‐Dm‐PBLG triblock copolymers. Their molecular structures and physical properties were characterized in detail by FTIR, NMR, gel permeation chromatography, differential scanning calorimetry, and wide angle X‐ray diffraction (WAXD). The crystallinity of the central PCL segment within these copolymers is increasingly suppressed by the flanking PBLG wedges, whereas the PBLG segments gradually changed from a β‐sheet conformation to an α‐helix conformation with the increasing PBLG branches. These triblock copolymers formed thermoreversible organogels in toluene, and the dendritic topology of PBLG wedges controlled their critical gelation concentrations. The self‐assembled structure of organogels was further characterized by means of transmission electron microscopy, WAXD, and small‐angle X‐ray scattering. The fibers with flat ribbon morphology were clearly shown, and the gelation occurred through a self‐assembled nanoribbon mechanism. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 709–718, 2010